An oscillator circuit, or simply “oscillator,” is an electronic circuit that generates a clock signal at a controlled frequency. A control circuit typically generates a control voltage that sets the output frequency of the oscillator clock signal. Both the oscillator and the control circuit are often manufactured in a single integrated circuit (“IC”) chip.
An oscillator control circuit typically uses resistive and capacitive devices to generate the control voltage. These devices have electrical characteristics that vary based on temperature and manufacturing process variations. During manufacture, oscillator control circuits often must be calibrated or “trimmed.” Trimming compensates for sources of temperature and process errors within the control circuit so that, during post-manufacture operation, the oscillator generates an approximately constant output clock signal frequency across temperature and process variations.
One current trimming technique involves physically heating an IC chip and trimming the oscillator control circuit at various temperatures such that the oscillator generates the desired clock frequency at each temperature. To trim the chip, a range of trim values for the control circuit are set on a trial-and-error basis until the desired output frequency is achieved at each temperature. This trimming technique, however, requires substantial time to both heat and sweep through all possible trim values for each temperature. Since trimming operations are prolonged, this trimming technique can become costly and time consuming and limit the number of ICs that can be manufactured per unit time.
Another current trimming technique involves manufacturing the resistive and capacitive devices within an oscillator control circuit according to precise manufacturing process specifications. This trimming technique, however, increases the manufacturing costs per unit IC.
Accordingly, there is a need in the art for an oscillator system that minimizes trimming time and compensates for temperature and process dependent error sources within the system.